Herein, the Applicant claims the priority of the filing date of a R.O.C. Application No. 099104083 filed on Feb. 10, 2010, and entitled “Electrostatic Discharge Structure for Touch Panel Module”.
At present, the touch control technology has been widely applied to various electronic devices or display equipment, and users can control the electronic device via merely moving his finger or a stylus to contact or approach the touch panel. Thereby, users can input data, read information, and interact with an electronic device in the most direct way. Thus, the touch panel not only exempts users from the inconveniences of inputting data with press buttons, a keyboard, or a joystick but also increases the pleasure of using an electronic device or display equipment.
According to different sensing principles, the touch panels can be categorized into the resistive type, the capacitive type, the infrared type, and the ultrasonic type. Refer to FIG. 1A. The conventional touch panel 1 normally comprises a cover lens 11 and a touch control layer 12. The touch panel 1 can be glued and attached to a display 2 to function as a touch control device. The upper surface of the cover lens 11 is an area where the finger/stylus contacts/points to. The periphery of the lower surface of the cover lens 11 has a pattern layer 13 and the lower surface of the cover lens 11 is stuck to the touch control layer 12 with optical glue 14. The touch control layer 12 has a transparent substrate 15 and a sensing layer 16 formed on the surface of the transparent substrate 15. Refer to FIG. 1B. In the example of the capacitive touch panel, the sensing layer 16 includes a plurality of arrayed sensing units (not shown in the drawing) respectively corresponding to the electric variations in the x-axis or y-axis directions. When the human body contacts the touch panel 1, the capacitance variations and inducted currents can be generated to calculate the coordinates and tracks of the contacted positions.
FIG. 1B is a diagram schematically showing the appearance of a touch panel module 3. The touch panel module 3 comprises a touch panel 1 and a circuit board 4 connected with the touch panel 1. The circuit board 4 includes a plurality of sensor chips 41, for example, the sensor chips 41 respectively corresponding to the x-axis and y-axis. In the touch panel 1, each sensing unit of the sensing layer 16 is electrically connected to the corresponding sensor chip 41 via a metallic wire 5, whereby the sensor chip 41 can receive and process the electric signals from the sensing unit and correctly judge the coordinates of the contacted point.
The touch panel 1 is likely to lead into static generated by contact and friction or conducted from the human body. When the touch panel 1 accumulates too many electric charges, electrostatic discharge (ESD) will occur and damage the electronic elements of the circuit board 4. However, the metallic wires 5 which electrically connect with the sensing layer 16 are not grounded lest the operation of the sensing layer 16 be affected. Besides, numerous metallic wires 5 are densely disposed on a connection portion 42 of the circuit board 4. Thus, intense ESD current is likely to go through the metallic wires 5 and flow into the sensor chip 41 to damage or burn out the sensor chip 41.
A R.O.C. publication No. 200901013 discloses an “ESD Touch Panel and Electronic Devices Equipped with the Same”, wherein an ESD protection circuit is installed on a touch panel, and wherein the ESD protection circuit forms a protective frame to direct away ESD current. However, the prior art mentioned above needs an additional circuit formed on the touch panel, which complicates the fabrication process, increases the fabrication time and cost and occupies the edge space of the touch panel. Therefore, the prior art has still room to be improved.